A Stirling engine is a closed-cycle regenerative heat engine with gaseous working fluid that converts thermal energy into mechanical energy. The Stirling engine can be driven by any source of heat and may exhibit a relatively high thermal efficiency. In addition to its thermal efficiency, the Stirling engine has been noted for its quietness of operation and its ability to utilize wasted heat. Moreover, in contrast to internal combustion engines, the Stirling engine may have the potential to use renewable heat sources more easily than standard engines. The Stirling engine may also have a greater reliability than internal combustion engines and have lower maintenance requirements. As a result, the Stirling engine has been a focus within industries involved with developing energy saving methods.
Recently, there has been some interest in using solar energy to provide heat for the Stirling engine. In such configurations, a solar collector, coupled to the engine, may be employed to collector solar energy in order to heat a working fluid in the engine. A solar collector may typically include a dish to receive solar energy and to concentrate the solar energy onto the engine. Notably, as the operating temperature of a Stirling engine increases, its efficiency in converting thermal energy to mechanical energy may also increase. In contrast, however, the efficiency of a solar collector may decrease with an increase in operating temperature. Such a decrease in efficiency of the solar collector may significantly temper the increase in efficiency of the engine. Therefore, a balance in operating temperature may need to be achieved such that both the solar collector and the Stirling engine may operate at relatively high efficiencies. Furthermore, reducing the size of the solar collector may also be desired to increase practicality and functionality while reducing the weight and cost of a system. However, a relatively smaller solar collector may provide less solar energy, and consequently less heat to the Stirling engine, thereby reducing the engine's efficiency.
Thus, a need exists for systems and methods for providing secondary thermal energy to the Stirling engine in addition to solar energy in order to improve the efficiency of the engine.